Prevailing building and safety codes such as the National Electrical Code of the National Fire Protection Association, which has been adopted by many states and municipalities, require that electrical wiring connections to electrical circuit devices from an electrical circuit or electrical conduit occur in an enclosed electrical outlet or junction box housing.
The electrical outlet box is available in a variety of styles and shapes, but each has a concave interior cavity with a substantially planar opening. Cover plates (also called face plates) for these boxes have openings of various standard sizes and shapes to accommodate the exterior interface portions of the electrical circuit devices. When the electrical circuit device is securely attached to the cover plate, the exterior interface portion of the electrical circuit device extends through these openings in the cover plate to create an uninterrupted cover plate assembly. This assembly may then be attached to the outlet box to serve as an exterior front wall and thereby create an enclosed housing.
FIGS. 1 and 2 illustrate a cover plate assembly 10 of a type found in the current art. For installation according to code, electrical junction boxes (not shown) must have proper covers. Whenever an installed junction box with electrified wires fails to have a cover, this is noted as an open junction box and considered to be dangerous, since it clearly constitutes a fire or electrocution hazard.
Cover plate assembly 10 as shown includes cover plate 12. For industrial applications, cover plate 12 is typically made of metal and, in particular, steel, galvanized steel, or aluminum. In non-industrial settings, cover plates are typically formed of plastic. Cover plate 12 has a face portion 14 and a mounting portion 16. Mounting portion 16 serves to fasten cover plate 12 to the junction box. Extending between face portion 14 and mounting portion 16 are four side portions 18. Face portion 14 has a planar exterior surface 20 and a planar interior surface 22; mounting portion 16 also has a planar exterior surface 24 and a planar interior surface 26; and each side portion 18 has a planar exterior surface 28 and a planar interior surface 29. Interior surface 22,26,29 cooperate to produce a concave aspect to the interior portion of cover plate 12.
To form cover plate assembly 10, a specific electrical circuit device 30 is attached to cover plate 12. Electrical circuit device 30, as shown, is a conventional, “off-the-shelf” duplex or double outlet electrical receptacle having two standard, grounded sockets 32 as its interface members. Each grounded socket 32 is exterior to cover plate assembly 10 by extending outward through a socket aperture 34 in face portion 14 and serves as an electrical outlet for users of cover plate assembly 10.
By convention, and for some electrical circuit devices by code, electrical circuit device 30 is attached to cover plate 12 by means of at least one plate screw 36. Plate screw 36 are commonly standard threaded connecting screws of a narrow shank. Electrical circuit device 30 has two attachment tabs (also called ears) 38 at the longitudinally top and bottom ends of its housing to receive plate screws 36. Each of the two plate screws 36 extends through a face-plate screw port (not shown) and through a tab screw port (not shown) in tab 38.
Tab 38 is integrally attached to electrical circuit device 30. Electrical circuit device 30 has energizable terminals 40. It is well recognized that energizable terminals 40 may be of a screw-type (as shown) or of any other means for attaching a live, electrifiable wire to the terminal such as through a spring-loaded terminal. Electrical circuit device 30 also has ground terminal 42.
Plate screws 36 are secured by plate nuts 44. Each plate nut is preferably a machine screw nut having a major plate-nut width wn. Between each plate screw 36 and the nearest side-portion inner surface 29 is clearance width wc. For a variety of reasons, including the cost of materials of production and the unintrusive, aesthetic nature of the finished installation, cover plate 12 is configured to have minimal facial area. To accomplish this, cover plate 12 is provided with side portions 18 that are narrowly spaced apart from tabs 38 when the exterior interface portions or sockets 32 of the electrical circuit device 30 are positioned within socket apertures 34. As a result, there is little clearance available for threading plate nuts 44 to plate screws 36. In typical installations of this type in accordance with the current art, wn is about ¼ in. and wc is about 3/16 in. Moreover, side-portion inner surface 29 has a depth dimension dsp of about ½ in.
Given the depth dimension dsp of side-portion inner surface 29 and the tight dimensioning of nut width wn within clearance width wc, the assembly of electrical circuit device 30 to cover plate 12 requires the assembler to not only hold electrical circuit device 30 in proximity to cover plate 12, but that he also simultaneously hold nut 44 with his fingers against tab 38 in alignment with the tab screw port while inserting a plate screw 36 through face-plate screw port and tab screw port so that it can be threaded through nut 44. Due to the dimensions of these components, such an assembly is difficult at best and will always be very time consuming. Industrial and commercial construction across the country require dozens, if not hundreds, of these assemblies at each site. Since electricians at all experience levels are usually paid at an hourly rate, the cost for assembling these cover plate assemblies 10 in the course of any electrification wiring job can be quite high.
A quick connection between a conventional electrical circuit device and a cover plate that facilitates easy and secure attachment thereto without the use of additional fasteners or modification to the circuit device itself would therefore constitute an important advancement for industrial and commercial electrical installations. The time saved when multiplied by the thousands of units installed each year equates to a substantial cost savings in addition to significant increases in overall productivity.